Inorganic Chemistry
ARTICLE
During complex synthesis, the acidity of the proton in the
backbone is further increased by the enhanced electron density
on the oxidized metal and it is lost easily. Thus, no reprotonation
is feasible, as with weak acids no reaction is observed, but strong
acids lead to immediate decomposition of the compound.
In the case of CuII complex 1 and its deprotonated derivative
4, EPR spectroscopy and DFT calculations reveal a rather
increased symmetry upon deprotonation. This becomes evident
from the transition of the nonaxial g tensor for 1 to an essentially
axial one for 4 and is in line with the presence of only one tightly
bound NO3ꢀ counterion. With the decreased number of ligands,
the overall symmetry is enlarged. This observation corresponds
to the elimination of ꢀhydrogen bonding between the ligand
and neighboring NO3 counterions that is present in [CuII
(PIPYH)(NO3)2] (1) (Figure 4).
General Procedure A (Synthesis of Complexes 1ꢀ3). To a
boiling solution of PIPYH in ethanol was added 1 equiv of the metal salt
[Ni(NO3)2 6H2O, Cu(NO3)2 3H2O, or Zn(NO3)2 4H2O] as a 0.1 M
solution in ethanol. A color change was immediately apparent. The
reaction mixtures were heated to reflux for an additional 20 min,
followed by cooling to room temperature. The products crystallized
overnight at ambient temperature by slow evaporation of the solvent.
The obtained crystals were isolated by filtration and dried in vacuo.
Synthesis of [CuII(PIPYH)(NO3)2] (1). General procedure A was fol-
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lowed by employing PIPYH (50 mg, 0.21 mmol) and Cu(NO3)2 3H2O
3
(0.21 mmol, 2.1 mL of a 0.1 M solution in ethanol) in 10 mL of ethanol;
compound 1 was obtained as green parallelepipeds (45 mg, 51%) by
crystallization at room temperature overnight. IR (ATR, cmꢀ1) ν = 1594
(w), 1486 (m), 1283 (s), 1010 (m), 930 (m), 778 (s), 417 (s). EI-MS (m/
z) 295 [M ꢀ 2NO3 ꢀ H]+. Anal. Calcd for CuC10H8N7O6Cl(Found): C,
28.52 (28.77); H, 1.91 (1.59); N, 23.28 (23.15).
Synthesis of [NiII(PIPYH)2](NO3)2 (2). General procedure A was
followed by employing PIPYH (50 mg, 0.21 mmol) and Ni-
’ EXPERIMENTAL SECTION
(NO3)2 6H2O (0.21 mmol, 2.1 mL of a 0.1 M solution in ethanol) in
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10 mL of ethanol; compound 2 was obtained as orange rectangular rods
(49 mg, 72% based on ligand) by crystallization at room temperature
overnight. IR (ATR, cmꢀ1) ν = 1594 (m), 1420 (s), 1136 (s), 897 (s),
839 (s), 770 (s), 640 (s), 571 (s), 418 (m). MS (ESI in CH3CN, m/z)
General. All chemicals were purchased from commercial sources
and used without further purification.
Spectroscopy. All NMR spectra were measured on a Bruker
Avance III spectrometer (300 MHz for 1H and 75 MHz for 13C NMR).
The 1H NMR spectroscopic data are reported as s = singlet, d = doublet,
t = triplet, m = multiplet or unresolved, br = broad signal, coupling
constant(s) in hertz, shifts in parts per million (ppm) relative to the
solvent residual peak. UV titrations were performed on a Varian Cary 50
spectrophotometer with a thermostated cuvette cavity. Infrared spectra
were measured on a Bruker ALPHA-P Diamant ATR-FTIR spectro-
meter. Mass analysis was performed on an Agilent Technologies 5975C
inert XL MSD direct insertion probe spectrometer applying electron
impact ionization.
525 [M ꢀ H]+. Anal. Calcd for NiC20H16N12O6Cl2 H2O (Found): C,
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35.96 (35.89); H, 2.72 (2.56); N, 25.16 (25.41).
Synthesis of [ZnII(PIPYH)2](NO3)2 (3). General procedure A was fol-
lowed by employing PIPYH (50 mg, 0.21 mmol) and Zn(NO3)2 4H2O
3
(0.21 mmol, 2.1 mL of a 0.1 M solution in ethanol) in 10 mL of ethanol;
compound 3was obtained as yellow cubes (54 mg, 78% based on ligand) by
crystallization at room temperature overnight. IR (ATR, cmꢀ1) ν = 1595
(m), 1424 (s), 1585 (s), 1147 (s), 782 (m), 414 (m). EI-MS (m/z) 530
[M ꢀ 2H]+. Anal. Calcd for ZnC20H16N12O6Cl2 0.4(EtOH) 2H2O
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(Found): C, 35.13 (35.13); H, 3.21 (3.20); N, 23.65 (23.62).
EPR spectra were taken on a MS300 (Magnettech, Berlin, Germany)
or Bruker EMX (Bruker, Rheinstetten, Germany) spectrometer. The
samples were kept at 77 K in a dewar finger filled with liquid nitrogen
(the spectra were taken at a modulation amplitude of 5 G). EPR spectra
were simulated with Simfonia (Bruker, Rheinstetten, Germany).
Synthesis of 3-Hydrazino-6-chloropyridazine.33 A solution
of 3,6-dichloropyridazine (2.0 g, 13.4 mmol) in water/NH3 (50 mL) was
heated to reflux when hydrazine hydrate (4.3 g of a 25% solution,
21.5 mmol) was added. Heating was maintained for 3 h, after which full
conversion was evidenced by thin-layer chromatography (TLC). After
the solution was cooled to room temperature, the volume was reduced to
one-third. Upon cooling the solution in an ice bath, the product
precipitated as a beige crystalline material, which was filtered off and
dried in vacuo to afford the product. (1.65 g, 85.2%). 1H NMR (300 MHz,
CD3CN, 300 K) δ = 4.11 (br s, 3H, NH-NH2), 7.12 (d, J = 9.3 Hz, 1H,
General Procedure B (Synthesis of Complexes 4ꢀ7). To a
boiling solution of PIPYH in ethanol was added triethylamine, and the
mixture was refluxed for 5 min. Subsequently 1 equiv of the metal salt
[Co(NO3)2 6H2O, Ni(NO3)2 6H2O, Cu(NO3)2 3H2O, or Zn-
3
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(NO3)2 4H2O] was added as a 0.1 M solution in ethanol. An intensive
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color change was immediately apparent. The reaction mixtures were
heated to reflux for an additional 20 min, followed by cooling to room
temperature. The products crystallized overnight at ambient tempera-
ture by slow evaporation of the solvent or were precipitated by layering
with diethyl ether. The obtained materials were isolated by filtration or
centrifugation and dried in vacuo.
Synthesis of [CuII(PIPY)(NO3)] (4). General procedure B was followed
by employing PIPYH (50 mg, 0.21 mmol), triethylamine (30 μL,
0.21 mmol), and Cu(NO3)2 3H2O (0.21 mmol, 2.1 mL of a 0.1 M
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ArHPdz), 7.29 (d, J = 9.3 Hz, 1H, ArHPdz), 7.50 (br s, 1H, NH-NH2). 13
C
solution in ethanol) in 10 mL of ethanol; compound 4 was obtained as
dark brown microcrystalline material (29 mg, 39%) by slow evaporation
of the solvent overnight. The material was washed with chloroform and
dried in vacuo. IR (ATR, cmꢀ1) ν = 1600 (m), 1434 (s), 1397 (s), 1284
(s), 1097 (m), 740 (s), 674 (s), 414 (s). MS (EI, m/z) 295 [M ꢀ NO3]+.
Anal. Calcd for CuC10H7N6O3Cl (Found): C, 31.93 (32.26); H, 2.41
(2.71); N, 22.43 (21.53).
NMR (75 MHz, CDCl3, 300 K) δ = 116.6, 129.2, 145.9, 162.2 (aromatic
carbons).
Synthesis of PIPYH. An ethanolic solution (60 mL) of 3-hydrazi-
no-6-chloropyridazine (1.00 g, 6.9 mmol) and 1.1 equiv of 2-pyridineal-
dehyde (0.73 mL, 7.6 mmol) in the presence of acetic acid (3 drops) as a
catalyst was heated to reflux for 45 min. After the mixture was cooled to
room temperature, the precipitated product was filtered off as white
needles and dried in vacuo to yield 1.21 g (75.1%) of PIPYH. 1H NMR
(300 MHz, CD3CN, 300 K) δ = 11.97 (s, 1H, NH), 8.57 (d, J = 4.9 Hz,
1H, ArHPy), 8.16 (s, 1H, HNdC), 8.03 (d, J = 7.9 Hz, 1H, ArHPy), 7.83
(t, J = 7.7 Hz, 1H, ArHPy), 7.76 (d, J = 9.4 Hz, 1H, ArHPdz), 7.71 (d, J =
9.4 Hz, 1H, ArHPdz), 7.35 (dd, J = 7.1, 4.9 Hz, 1H, ArHPy). 13C NMR (75
MHz, DMSO-d6, 300 K) δ = 116.6, 119.8, 124.0, 130.6, 137.1, 142.8,
148.4, 149.8, 154.0, 159.2. EI-MS (m/z) 233 [M]+. IR (ATR, cmꢀ1) ν =
1576 (m), 1529 (m), 1461 (m), 1407 (s), 1284 (m), 1070 (s), 830 (s),
769 (s), 713 (s), 426 (s).
Synthesis of [NiII(PIPY)(PIPYH)](NO3) (5). General procedure B was
followed by employing PIPYH (50 mg, 0.21 mmol), triethylamine
(30 μL, 0.21 mmol), and Ni(NO3)2 6H2O (0.21 mmol, 2.1 mL of a
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0.1 M solution in ethanol) in 10 mL of ethanol; compound 5 was
obtained as dark brown microcrystalline material (31 mg, 50% based on
ligand) by slow evaporation of the solvent overnight. The material was
washed with chloroform and dried in vacuo. IR (ATR, cmꢀ1) ν = 1597
(m), 1401 (s), 1290 (s), 1124 (s), 1033 (m), 746 (m), 653 (m). MS (ESI
in CH3CN, m/z) 525 [M]+. Anal. Calcd for NiC20H15N11Cl2O3
CHCl3 (Found): C, 35.71 (35.69); H, 2.28 (2.22); N, 21.81 (22.01).
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dx.doi.org/10.1021/ic200279g |Inorg. Chem. 2011, 50, 7478–7488